Virtually all electronic devices manufactured today include one or more circuit boards or related hybrid circuits (hereafter jointly referred to as circuit boards). The individual electronic components are mounted on the circuit board and interconnected by ribbon like electrical conductors on the circuit board itself. Such circuit boards have traditionally used through hole technology wherein the electrical leads from the components extend through the board and are soldered to the board conductors on the lower surface of the board. More recently, surface mount technology has become widely utilized wherein the electrical leads or contacts from the component are soldered directly to the board conductors at the upper surface of the board.
In mounting the individual electronic components on a circuit board, the various leads from the component are soldered to conductors on the circuit board. This soldering process leaves rosin and organic fluxes on the circuit board, potentially giving rise to electronic shorts across the various conductors. Other contaminants which can effect performance include oils, greases, fingerprints and non-specific particulate matter.
To remove the rosin, flux, or other contaminants remaining on the board after soldering, the board is typically washed by running the board through a cleaning machine which sprays a solvent or water on the board to remove the contaminants. The cleaning device commonly has a continuous conveyor belt which conveys the board through the machine past the solvent wash, past a rinsing wash, and finally a drying stage. Apparatus of this type are constructed and sold by Electrovert U.S.A. Corp., of 4330 Beltway Place, Arlington, Texas 76018, which includes their model Century 2000C Water Cleaning System and the system H500 Hydrocleaner. U.S. Pat. No. 3,868,272 relates to the Century 2000C Water Cleaning System. Other suppliers of this type of equipment include: Genesolv/Boron-Blakeslee, 1 Gate Hall Drive, Parsippany, N.J. 07054; Detrex Corp., P. 0. Box 5111, Southfield, Michigan 48086; Corpane Industry, 250 Production Court, Louisville, Kentucky 40299.
These devices use a conveyor belt to guide the circuit boards through various stages of cleaning. Because the electronic components are often mounted so close to the circuit board, often with only a two to four thousandths of an inch gap between the component and the board, the use of water alone has been found insufficient to adequately clean the boards because of the high surface tension of the water. It has thus become necessary to use chlorinated and fluorinated solvents in the initial washing stage to adequately clean the boards. However, these solvents are expensive and hazardous. In fact, the Environmental Protection Agency has established regulations which phase out the use of such solvents beginning in 1993.
A need thus exists for an improved cleaning system which adequately cleans circuit boards while drastically reducing, and possibly even eliminating the use of expensive and toxic solvents. Further, a need exists for a cleaning device which is capable of effectively cleaning between a component and the board when the gap between them is as little to two to four thousandths of an inch.